The timing controlling unit is generally used in the display controller. In the controller, the buffer unit is necessary. For example, while Over Drive (OD) technology is applied, the frame buffer is required. The conventional buffer unit is integrated with the timing controlling unit while packing process. In other words, the timing controlling unit and the buffer unit are fabricated individually and integrated while packaging. The package process is complicated and the cost is high as well. With the upcoming high definition resolution technology, the resolution of the image is higher and higher and the buffer unit needs to process more and more data with certain algorithm. Therefore, the cost of the buffer unit is higher as well. Meanwhile, the timing controlling unit, the buffer unit, the power management unit and other functional unit are disposed on one circuit board in the conventional controller. The size of the circuit board is larger and requires a specific space to dispose in the display device. This makes the display device big, heavy and high cost.